Measuring UHI on a bike produces a new paper

While NCDC’s Dr. Thomas Peterson tries to ignore UHI, from Hans Von Storch at Die Klimazwiebel (h/t to Jos de Laat) we learn that many other people are actively measuring it. WUWT reader may remember my “do it yourself UHI kit” for vehicles…now there’s one for a bike:

It is long known that in cities there may be a significant climatic effect due to urbanization – thus in cities we have the interesting and challenging task of determining at least three significant drivers for change, if not more, namely the effect of the local modification of the environment as well as the local manifestation of global change due to greenhouse gases (plus, possibly other global factors). Unfortunately, systematic studies about the determination and separation of these effects – in principle a detection and attribution task – have not been done often. At least, I am not aware of such efforts; indeed even studies only on the size and distribution of the urban heat island effect (UHI) are not done often; in Hamburg, a first study was only published in the last few years – before that one could hear that in a maritime climatic environment as Hamburg, the effect would be negligible. It is not.

Now, an innovative study is about to be published – see the manuscript here: Measurement and statistical modeling of the urban heat island of the city of Utrecht (the Netherlands) by Theo Brandsm and Dirk Wolters from KNMI. The trick was, to do the year long observations by bike, as described in this abstract:

Mobile temperature and humidity measurements have been performed along a 14 km transect through the city of Utrecht (311,000 inhabitants) in the period March 2006 – January 2009. The measurements took place on a bicycle during commuter tra c and resulted in 106 nighttime profiles (before sunrise) and 77 daytime (afternoon) profiles. It is shown how the intensity of the urban heat island depends on wind direction, cloudiness and wind speed. Statistical models are constructed that relate the mean and maximum nighttime urban heat island intensity profiles to area-averaged sky-view factors and land use combined at both the micro and local scale. Sky-view factors are estimated from a 0:5 x 0:5 m surface elevation database and land use is obtained from a 25 x 25 m land use database. The models are calibrated using the mobile measurements and provide estimates of the spatial distribution of the mean and maximum nighttime urban heat island intensity in Utrecht. Both models explain more than 75% of the variance. A separate non-linear model is introduced that relates the temperature differences between the warmest and coolest part of the transects to wind speed and cloudiness.

The paper:

Brandsma, T. and D. Wolters, Measurement and statistical modeling ofthe urban heat island of the city of Utrecht (the Netherlands)
Journal of Applied Meteorology and Climatology, 2012, 51, 1046-1060.

58 thoughts on “Measuring UHI on a bike produces a new paper”

I used to be in the asphalt business and within that industry is COMMON KNOWLEDGE that asphalt road surface temperatures can COMMONLY be 20F to 30F HIGHER than ambient air temperatures, even on cloudy days. On hot sunny days, the asphalt can easily attain temperatures greater than 30F warmer than ambient.
It is no secret that asphalt is a very good “storer” of heat as is, of course, roofing tar.
Of course, concrete and steel exhibit similar properties, though to a lesser extent.

It may be that it had not attracted my attention previously, but I have noticed of late that the MET Office in the UK in the guise of their TV weathermen now often openly talk about overnight rural temperatures being 3 or 4 degrees or even 5 degrees C cooler than overnight urban temperatures. Is this perhaps because they can now get away with the statement without it being tied to UHI measurement bias because they are the authority and they have the media tied around their little fingers, or are they just p**d off with their alarmist superiors in the Climate department?

Research is confirming what common sense clearly suggests.
The good thing is it’s telling us that in an average Northern European urban environment the effect is responsible for up to 2°C.
How much will it be in Phoenix AZ or LA or Dallas TX, and how much under airport conditions?
Probably the most underestimated factor in measuring temperatures.
So AGW has always been an engineering issue (how to measure temperatures) and activist-scientist have been jumping on wrong data to promote their cause. For more than 2 decades now.
What a desaster.
Anthony, surfacestations.org has been right on the money, from the beginning.

That is a massive amount of work over a long period to come up with something that substantiates common sense. If I put ten 100 watt light bulbs in my living room, turn them all on, it will soon become the warmest room in the house; my own self-made UHI. Now all we need to do is apply the model to all the UHI temps as an adjustment. Raw compared to the model.

The main cause of the daytime UHI is restriction of convection. Because convection and radiation are coupled, the local temperature increases to maintain, at equilibrium, constant convection + radiation. Try it on the beach with a wind break to demonstrate the principle to yourself. This experiment also proves the earth cannot emit IR as if it were a black body because otherwise the temperature would not rise to generate the extra radiative heat loss!

A secondary cause is there is less evapo-transpiration so less of the convection is via the generation of latent heat in the atmosphere by increasing its humidity. The third reason is that the heat capacity of dense structural materials is higher than less dense soil, so there is more sensible heat storage.

It would be interesting to attach one of the do it yourself devices or use existing temperature data from the airlines data recorders to map temperatures in and around UHIs as well as any other long term data on temperature trends globally. Who needs a balloon, when we already have thousands of air-penetrating devices zooming about the heavens.

I don’t know about the accuracy of their model but can tell you that on a motorcycle the changes in temperature are very apparent when riding in the city or in rural areas, for that matter, and are significant. Lower elevations in rural areas, in particular, collect cold air and in Phoenix, in particular, when one enters irrigated highly built areas the humidity amplifies the heat SUBSTANTIALLY when riding through in 100+ F temps. Concrete and asphalt pavement, roof tops, AC exhaust, overhead haze from sewer exhaust on every roof (methane), etc.

Elimination of significant portions of the human population would go a long way to mitigating what little insignificant portion of heating is man made on this planet, though it would do nothing to alter whatever direction the historical, continuous climate change is taking. And warm is better than cold, in any event.

UHI? Oh I remember, that’s the thing that the UK Wet Office said doesn’t exist, doesn’t affect their temperature records, it does exist but it’s been allowed for, oh & it’s going to kill us all by 2100AD because of Global Warming! Dr Vicky Pope rocks, doesn’t she just! Curiously, she & Dr Julia Slingo seem to have been particularly quiet of late, something’s afoot me thinks!

I have long noticed that the trees in the city and suburbs turn color later in the fall than do trees out in the country, because of the nearby streets and buildings holding in the warmth of the day overnight.

“I don’t know about the accuracy of their model but can tell you that on a motorcycle the changes in temperature are very apparent when riding in the city or in rural areas, for that matter, and are significant.”
I’ve noticed the same thing here in Ohio, there’s even a big difference in sunny areas vs areas where the sun is blocked.
But I’ve also got thermometers at the house, the one that’s blocked from the wind, but in direct sun over brick can easily get over 120F on warm sunny days. And while it drops quickly when the sun goes away (and sets), the bricks are still warmer than air temps after cooling all night.
What I don’t understand is how scientist who say there’s no apparent UHIE come to that conclusion, do they never go out after dark, never leave/visit a city? It boggles my mind.

Colin Porter says:
October 10, 2012 at 8:37 am
It may be that it had not attracted my attention previously, but I have noticed of late that the MET Office in the UK in the guise of their TV weathermen now often openly talk about overnight rural temperatures being 3 or 4 degrees or even 5 degrees C cooler than overnight urban temperatures. Is this perhaps because they can now get away with the statement without it being tied to UHI measurement bias because they are the authority and they have the media tied around their little fingers, or are they just p**d off with their alarmist superiors in the Climate department?
__________________
The most likely reason that you’ve only just noticed it is that it’s most pronounced when rural areas experience a frost but urban areas stay above freezing. During summer the differences don’t get commented on.

Other minor problem of urban settlements is they are often in uncharacteristically warm spots anyway (at least in temperate areas). If you look at the siting of any old (pre-1000) church site in Scotland, it is likely to be notable warmer than surrounding areas. I suspect the same is true for successful early North American settlements.

So in those areas which get cold, it may be the least cold places are where people built important settlements, which are often still the largest settlements…

The problem with discerning UHI in the temperature record is that it has built up slowly, over decades, as the cities grew. If each city had instantly appeared over night, the UHI for that city would be obvious in the temperature record and near impossible to argue about.

Which brings up an interesting question.

It is my understanding that China is building entire cities from scratch, often evicting families from multi-generation farms to do so. Any chance that they are making before and after temperature records?

I hate to rain on the parade, but if UHI now is no worse than it was 20 years ago, then the temperature trend has not been affected. I suspect that since major urban centers continue to be survivable that UHI is a limited phenomenon, detectable while a city is growing from a cow pasture, but insignificant past a certain level of development. So only cities smaller than a certain size will experience a temperature trend affected by UHI. The New York Central Park temperature record supports this.

David “Just look at this as a UHI example!;http://ceo.decc.gov.uk/nationalheatmap/Click on ‘layers’ – ‘total heat’ ”
It looks great, but sadly its just colourings based on guessed energy consumption.
Thanks for the link though.

Sorry pochas but you are incorrect. As more and more rural temperature stations are encroached upon by man made structures those once rural stations will show warming. The alarmists will use that as “proof” of global warming. And even a mature city still experiences land use changes. Older homes with larger yards being torn down and replaced with smaller houses grouped closer together leaving less green space around them.

I believe a control experiment for the measurement of UHI exists in the form of my home city of Christchurch, New Zealand (population c. 375,000). On 22FEB11 we had an earthquake which led to the immediate evacuation of the entire city centre (still largely unpopulated). I don’t have the expertise to conduct this study, but I offer it to anyone who does.

Matt: “How many US Cities have experienced no poplulation growth over the last 100 years?”

Maybe already, but certainly by 2020, Detroit will have shrunk to a lower population than 100 years ago. Detroit experienced both rapid growth and decline during that time. I hope temperature records pre- and post-decline are available.

That is a massive amount of work over a long period to come up with something that substantiates common sense. If I put ten 100 watt light bulbs in my living room, turn them all on, it will soon become the warmest room in the house; my own self-made UHI. Now all we need to do is apply the model to all the UHI temps as an adjustment. Raw compared to the model.

I tried that but the room was so bright I couldn’t read the thermometer!

October 10, 2012 at 8:41 am“Biking in Holland, who would have ever thunk it?”

But of course! And Holland is famous the world over for its breathtaking mountain biking. (Wait up! I may have something wrong there… nevermind.)
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All that sampling anywhere a bike can go. Good thinking.

I think this is a very interesting problem with much more to be discovered. Watchman’s remark raises a very interesting point. Many local variations, from whatever the cause, could make prefered sites for dwellings naturally “biased” for warmer temperatures. I guess there certainly could be a bias for selecting cooler locations in hot climates. But, to the point, I recall one morning when the radio reported temperature was -10 degrees F for the local urban location. On that particular morning I was out early and noted that in my suburban location my thermometer gave a reading of -17 degrees F. I left the house and drove across the valley and, in my “calibrated” Dodge truck thermometer, I noted a 5 mile wide pocket of air in the low lying area along the local creek drainage of a whopping -22 degrees F! I have found that routinely it can be -16 degrees F in a duck blind on the Platt river but the reported temperature for the day is barely below zero. The settlers knew that a little elevation and protection from the wind made for a more comfortable winter experience. Add some concrete and tall buildings and it becomes warmer still.

What this study shows is that there is an urban heat island within urban areas. No surprise really. The road pedaled here has not gone outside urban parameters, except for a short stretch just before they got to work where it is less built up. What this clearly shows is that the centre of this city with more offices, traffic, narrow streets, is warmer then the area where they started and finished which have slightly wider roads and a lower population density. There is no attempt made to travel from the temp station at De Bilt, the end point of the cycle trip and a major dutch weather station, to get into the real country side.
I know that in the Netherlands that would be a hard task but within 20 km of either end or starting point there is space that is classified as rural. This will have show a better extent of UHI, for the dutch situation that is, we do need to keep in mind that that country is so build up that a real comparison is virtually impossible to get.

Pochas has a point but only if nothing near the weather station would have changed in those 20 years. A new 25 level office block within 300m will have an effect on any reading, etc. Most of the temp stations that are used today show a lot more development around it compared to even 20 years ago.

A couple of months ago Anthony suggested that a human in an unheated, heavily insulated hut, in Antarctica sitting there trying to keep warm had an effect on a thermometer housed several metres away. I would like then to know what the effect of a hot sweaty human several inches away has on these results in his opinion?

pochas says:
October 10, 2012 at 10:44 am
I hate to rain on the parade, but if UHI now is no worse than it was 20 years ago, then the temperature trend has not been affected. I suspect that since major urban centers continue to be survivable that UHI is a limited phenomenon, detectable while a city is growing from a cow pasture, but insignificant past a certain level of development. So only cities smaller than a certain size will experience a temperature trend affected by UHI. The New York Central Park temperature record supports this.

It is intuitive that there is likely a limiting case for the UHI effect. But urban areas are not static. Consider an idealized urban center, with the heaviest positive influences concentrated at the core and diminishing monotonicly to the edge. In this case we suppose that at the center dT/dt as far as UHI goes is zero; no increase in positive influences will yield increases in the UHI effect. The temperature record at this location from then on will be a true reflection of the regional trends, all other things being equal (though we know they aren’t). This urban area is experiencing an annual population growth of 3.5%. Using the “rule of 70” and assuming that UHI influences grow at the same rate, the population and the UHI drivers will double in 20 years. Since it’s very difficult to grow services, housing, and employment in the congested center, the urban area will grow at the edges and in any underutilized interior areas. As the UHI factors increase, they increase the slope of the temperature record at the various historic sites.

An area started as a farm field, with a COOP station 100 ft from the house. The farm was sold, subdivided and developed. Now there is a wall within 25′ in every direction. Several properties are consolidated and an apartment building goes up with the station at the edge of the parking lot. More properties are consolidated and a strip mall is located on one side of the apartment building and a professional center on the other. The apartment building and strip mall are torn down, and a 12-story office building is erected. Now the station occupies a small plot in the middle of a very large parking lot. The professional building comes down and a 30-story financial center goes up and the parking lot is now a parking garage and the station is located on top, utterly surrounded by asphalt and concrete. Additional 20- and 40-story buildings are raised on surrounding plots until there is hardly a stitch of the natural world to be found within 1000′.

At the start, temperatures were in their natural state, but each change in land use added 0.1 degrees here, 0.05 degrees there until you top out at about 4-7 degrees C (let’s say). If your development happens to coincide with a natural upturn in the regional temperature trend, you would conclude that not only was it getting warmer, it was getting warmer faster, because thermometers in the underutilized areas were getting jacked up, and as time goes on there would be more of the thermometers showing a trend because portions of the area are showing increased UHI influences and the area is growing.

This is the thing that the data massagers don’t take into consideration. Their corrections are made without consideration of the time element involved. As far as they seem to be concerned, if there’s UHI effect today, it was there 50 years ago so we’d better cool the past. Me, I think it’s just laziness. You have to be seriously OCD to try and work that all out; someone like Chiefio, say ;-).

The population of Utrecht has grown from 100,000 in 1900 to 200,000 in 1950 to 230,000 in 2000 and finally rapidely growing to 316,000 nowadays. The larger area, once rural around the city, nowadays has over 600,000 inhabitants (the city included).

The Bilt was once a small village, but it did grow from 17,000 in 1945 to 33,000 in the nineties to 42,000 nowadays…

The KNMI meteoroligical station started in 1897 at The Bilt, outside the village. Now it is already at the edge of the village and in the main downwind direction of a growing Utrecht. One can only wonder how much the station, even as it is well sited in itself, is affected by the increasing population density in the surroundings.

The same for the KMI in Belgium, situated in Ukkel, once a rural place far from Brussels, now completely surrounded by houses of the Brussels agglomeration… There too, the temperature measurements are perfectly situated, with only grass around for some distance. But still…

That would be like saying that Mpls/St. Paul has had “zero” population growth, as from 1970 to now..THEY HAVE had ZPG!!! However, the metro area, since 1970, has gone from about 1.2 Million residents to over 3.5 million. A considerable EXPANSION of the original UHI….

Same with St. Louis. GET REAL, get your HEAD OUT OF THE SAND. Sorry, I guess I don’t tolerate fools lightly.

And how accurate is this setup? Rider gasping for breath and breathing all over the detector. More unwanted heat.
UHI despite being a true effect of cities and towns will be different for every area under consideration. This in itself would render the effect unquantifiable and unmodelable.

Hmm. So if you are travelling for some period of time during the day or night, and you do this in a consistent diection, how do you prevent the normal temperature variations during the day-night cycle from producing misleading UHI values?

“How many US Cities have experienced no population growth over the last 100 years?”
Saint Louis has a population of about 800,000 in the 1930′s and is now about 400,000. Other examples can be found.
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City limits are not real physical limits. So the real question is, what is the population of the county St Louis resides in from 1930 to present? Ever heard of suburban sprawl?

[ It is shown how the intensity of the urban heat island depends on wind direction, cloudiness and wind speed.]

Urban areas are producing, absorbing and radiating energy regardless of of the above three parameters, which only cause dispersion. Therefore, it appears they are measuring only a portion of the process. Still significant.

Next question: Where on this view are the stations whose temperatures are used by GISS, etc?

Just loo at the paper. The Meteo site is next to the spot maned KNMI at km 13.4.
That’s the place with the “negative deviation” – uuups?!?!
And I thought we got ‘em ;-))

Really?? Since the scale STARTS at +0.1, I wonder how that can be? Using my finely calibrated Mark 1 eyeball and the browser zoom feature, it appears that the deviation is not less than POSITVE 0.4 and no more than POSITIVE 1.5. But thanks for pointing out the location.

I was referring to the T-graph in the paper along the transects.
In the graphs of the analyzed transects the KNMI temp are well below the rest of the transect.

I guess you were referring to Picture whit the title:
Spatial distribution of the mean nighttime UHI
intensity for the city of Utrecht and its surroundings as
_calculated from the model_ in Equation 4 with respect to
the _rural background_ temperature.

MFKBoulder says:
October 11, 2012 at 12:58 pm
I was referring to the T-graph in the paper along the transects.
In the graphs of the analyzed transects the KNMI temp are well below the rest of the transect.

I guess you were referring to Picture whit the title:
Spatial distribution of the mean nighttime UHI
intensity for the city of Utrecht and its surroundings as
_calculated from the model_ in Equation 4 with respect to
the _rural background_ temperature.

Yes, over the length of the transect, at the KNMI location, the anomoly with respect to the transect appears to be about -0.25 during the day and -0.75 at night. But if the transect as a whole is 1-2 degrees above the surrounding rural area, then the KNMI location is just less hotter; it’s still biased “hot” when the data goes in the GISS mill. The nightime model thermograph would seem to support that conclusion.

D. J. Hawkins says:
October 11, 2012 at 4:29 pm
…
Yes, over the length of the transect, at the KNMI location, the anomoly with respect to the transect appears to be about -0.25 during the day and -0.75 at night. But if the transect as a whole is 1-2 degrees above the surrounding rural area, then the KNMI location is just less hotter; it’s still biased “hot” when the data goes in the GISS mill.

What brings you to the idea that the whole transect is 1-2 degrees (°C I assume) above the Rural back ground”. Rural background is a term which should be clarified in a state like the Netherlands with a population density (for the whole state) being higher than the one in the Boston SMSA

MFKBoulder says:
October 12, 2012 at 12:44 am
D. J. Hawkins says:
October 11, 2012 at 4:29 pm
…
Yes, over the length of the transect, at the KNMI location, the anomoly with respect to the transect appears to be about -0.25 during the day and -0.75 at night. But if the transect as a whole is 1-2 degrees above the surrounding rural area, then the KNMI location is just less hotter; it’s still biased “hot” when the data goes in the GISS mill.

What brings you to the idea that the whole transect is 1-2 degrees (°C I assume) above the Rural back ground”. Rural background is a term which should be clarified in a state like the Netherlands with a population density (for the whole state) being higher than the one in the Boston SMSA

If you follow the route of the transect on the thermal map, by inspection it doesn’t appear to have any significant length passing through an area less than 1.5 degrees above the lowest areas displayed. One may cautiously assume that truely rural areas in the Netherlands, as opposed the lower temperature areas immediately adjacent to the urban zone, are even cooler.

Before dismissing the likelyhood of the existence of such areas, let me point out that I live in New Jersey, USA and using Wikipedia entries as the bench mark, we are even more urban (459/km^2 vs 397/km^2), and I can assure you there are plenty of very rural areas left in the state. We raise more horses than Kentucky. As for the Boston SMSA (Greater Boston Area), Wiki gives the population density as 947/km^2. A little more than the Netherlands, ja? But thanks for playing!

“…certainly by 2020, Detroit will have shrunk to a lower population than 100 years ago. Detroit experienced both rapid growth and decline during that time. I hope temperature records pre- and post-decline are available.”

I wouldn’t think the concept works quite as well in reverse. I mean: as a city’s population decreases they’re hardly going to start ripping up the concrete structures and replace them with fields are they?

“I wouldn’t think the concept works quite as well in reverse. I mean: as a city’s population decreases they’re hardly going to start ripping up the concrete structures and replace them with fields are they?”

Nature itslef will do this if the area remains depopulated long enough. This process does take a lot longer than building the city in the first place though.

“I wouldn’t think the concept works quite as well in reverse. I mean: as a city’s population decreases they’re hardly going to start ripping up the concrete structures and replace them with fields are they?”

Nature itslef will do this if the area remains depopulated long enough. This process does take a lot longer than building the city in the first place though.

It might not take as long as you think. As the neighborhoods thin out, the city is trying to get people to consolidate, offering incentives to relocate. Then they cut off services to entire blocks. I think they’ve even bulldozed a lot of the now-empty houses. Once you fill in the foundation, you’ve got an open field. Emotionally wrenching for residents, but what can you do? It’s too expensive to keep services going when only 2 out of 20 houses on a block are occupied.